At first glance, the illusion looks like a blurry photo of Ben Stiller's Zoolander character from his 2001 movie of the same name. But if you squint your eyes, Stiller's face seems to disappear; in its place, Beyoncé's face materializes. Her face also appears more clearly, compared to Stiller's face, when you look at a smaller version of the image or stare at it from a distance.

2/

The Zoolander-Beyoncé photo is a variation of a simple optical illusion known as a "hybrid image."

One famous example of a hybrid image overlays the faces of Albert Einstein and Marilyn Monroe, as seen above. As Aude Olivia, the principal research scientist at MIT's Computer Science & Artificial Intelligence Lab, previously explained to Wired, this illusion is often used to study how our brains process visual stimuli and sight.

According to Olivia, who has created and used hybrid images in her research for decades, our eyes see "resolutions with both high spatial frequencies (sharp lines) and low ones (blurred shapes)." Up close, we focus on features with high frequencies, such as wrinkles or blemishes. But from a distance, sharp details become less visible and we instead register features with low frequencies, such as the shape of one's mouth or nose.

Hybrid images work by combining the high frequencies from one photo with the low frequencies from another. The result is a picture that can be perceived in two different ways, depending on the distance from which you look at it.

Advertisement

3/

If you focus on this image for about 30 seconds, it'll disappear completely.

In April 2018, an eye-care practice in Horsham, Pennsylvania, tweeted an optical illusion that left some people in disbelief. The image, posted by Dr. David McPhillips of Primary Eye Care Associates, disappears after approximately 30 seconds, when you focus on just one fixed point in the graphic.

So how does it work? Well, this mind-boggling effect is actually a variation of a famous optical illusion called Troxler's fading circle. Discovered in 1804 by Ignaz Troxler, a Swiss physician and philosopher, the Troxler effect illustrates the human brain's efficiency.

In simplest terms, your sensory neurons tend to filter out information that is constant — stimuli that your brain has deemed non-essential and non-threatening. As Live Science's Brandon Specktor explained, this ability to adapt quickly to stimuli allows your brain to focus on things that are actually important.

When you force your eyes to focus on one point, the way you do with Troxler-style illusions, your brain receives no new information to process. At this point, stimuli in your peripheral vision take on the nature of their surrounding environment — in this case, a white background — as your brain "fills in" information it has deemed unimportant to process.

4/

This person's tattoo makes it appear like he has a giant hole in his arm.

What color is this dresser?

In December 2017, Reddit user agamiegamer posted a photo of this dresser to the subreddit r/blackmagicf---ery. "What color do you see: pink and white or blue and gray?" the user titled the post.

People were immediately torn, with some seeing pink and white, others seeing blue and gray, and a few seeing "very light blue-green and pink" or "lime green and gray."

Eventually, Reddit user agamiegamer revealed the dresser was actually painted blue and gray in real life. When some were still skeptical, Reddit user romeroleo offered the following explanation: The "reddish" lighting of the photo makes the "unsaturated gray" parts of the dresser appear pink. The lighting also "warms" the "cold" blue parts of the dresser, which makes them appear white.

But look closer and you'll realize that it actually has a hidden "3D" kitchen.

Creative director Felipe Salazar and graphic designer Karen Castañeda recently turned a newspaper into an ad for HiperCentro Corona supermarket. The two artists manipulated the paper's text to look like a "3D" kitchen, using their design to add the illusion of depth. In reality, the paper is completely flat.

8/

Although you may see a bunch of swirling circles, this image is actually completely still.

The image above was inspired by the famous illusion "Rotating Snakes," created by Japanese psychologist and professor Akiyoshi Kitaoka in 2003.

Both are examples of a peripheral drift illusion, in which we perceive still images as moving ones. Interestingly enough, when you stare at one part of the photo without moving or blinking your eyes, that part stops "swirling" (while the circles in your peripheral vision continue to "move").

Is this cat going up or down the stairs?

This innocent photo of a cat went viral back in 2015 as people wondered whether the animal was going up or down the flight of stairs.

Internet users used everything from architecture to biology to defend their answers to the hotly debated question. INSIDER's Megan Willett, for example, broke down why the cat is "definitely" going down the stairs — and after reading her explanation on Business Insider, I'm convinced.

Called the "checker shadow illusion," the effect has to do with the way our brains interpret color and shadow.

As Slate explained, "your brain is always comparing things." Square A is surrounded by lighter squares, making it appear darker, while Square B is surrounded by darker squares, making it look lighter. The shadow also "messes with your perception" and "amplifies the effect," Slate added.

If you're still not convinced, open the image in Photoshop, use the Dropper or Color Picker tool to select the color in Square A, and draw a straight line to Square B (or vice versa).

MIT also has a great resource that explains the science behind this phenomenon.

14/

Is this shoe pink and white or teal and gray?

Earlier this month, this humble shoe went viral after people started debating whether it was pink and white or gray and teal. It felt like the second coming of The Dress debate from 2015, in which the internet could not agree on the true color of a bodycon dress.

Advertisement

15/

The shoe is actually pink and white in real life.

Just like the photo of The Dress, the original photo of the sneaker was taken in poor lighting with a bluish tint, INSIDER's Susanna Heller explained. Your perception of the shoe's color depends on your individual sensitivity to the lighting in the image.

In simplest terms, it all has to do with how your brain processes color. Basically, light bounces off objects in the world and reaches your eyes in "a mix of wavelengths," which your brain then interprets as color.

As Slate's Pascal Wallisch explained, "this mix depends on two things: the color of the object and the color of the light source. [...] To achieve what color vision scientists call 'color constancy,' the brain calculates color-corrections for an image on the fly. It takes note of the illuminating light and tries to figure out how it might be affecting the color of an object."

Since the photo of the dress was taken in poor lighting with a bluish tint, your brain either sees the dress in shadows (and color-corrects the dress to be white and gold) or in "a fair amount of illumination" (and perceives the dress as blue and black).

18/

Here's another example of color constancy: these strawberries aren't red.

The color red has been completely removed from the image, yet people still see red strawberries. Why?

Well, as INSIDER's Jacob Shamsian explained, the brain "knows that the color of an object is more useful than the color of a light source" in determining the color of an object. Thus, "it's trained to ignore information" it receives about the color of a light source. Since your mind recognizes that the objects in this photo are strawberries, and it knows that strawberries tend to be red, it color-corrects the gray and green pixels in the image to be red.

There are a total of 12 black dots in this image, but you can't see them all at once.

First published in 2000 in the academic journal "Perception" by Jacques Ninio and Kent A. Stevens, this illusion went viral after Professor Kitaoka shared it on Facebook and game designer Will Kerslake‏ reposted it on Twitter.

While you should be able to see any dot you look at directly, the dots in your peripheral vision seem to appear and disappear. Why? Well, in simplest terms, our peripheral vision sucks.

Similarly, this carpet looks like it's full of giant sinkholes.

In September, Twitter account @WHS_Carpet— which specializes in calling out "bad carpets" — brought this disorienting photo to the internet's attention. While the floor is completely flat, the carpet's designer added large spaces between certain lines to add depth and create a crater-like effect, INSIDER's Jacob Shamsian explained.

This famous image was named the "café wall illusion" by psychologist Richard Gregory in the 1970s. It's a classic optical illusion that dates back to the late 1800s. You can learn about the science behind the phenomenon in Gregory's 1979 paper here.

The glass orb that Christ is holding doesn't distort light the way it should in real life.

"Solid glass or crystal, whether shaped like an orb or a lens, produces magnified, inverted, and reversed images," writer Walter Isaacson explains in his biography of da Vinci. "Instead, Leonardo painted the orb as if it were a hollow glass bubble that does not refract or distort the light passing through it."

It's an especially strange choice given the artist's otherwise careful — and scientifically accurate — depiction of light in his works. That said, Isaacson, and many others, still believe that the painting is authentic. Perhaps, some have argued, da Vinci intentionally ignored physics in order to highlight Christ's divine powers.

The Guardian article is also now the subject of a legal complaint made on behalf of Christie's International Plc, the auction house that is due to sell "Salvator Mundi" later this year on November 15.

The neon blue lines make it appear like there is a light blue circle in the middle of this image, but the background is white throughout.

Known as "neon color spreading," this classic optical illusion was first documented in 1971 and later rediscovered by H.F. Van Tuijl in 1975. While the exact causes of this phenomenon are still unclear, you can read about several theories here.

32/

This photo of Kendall Jenner, Kylie Jenner, and Hailey Baldwin went viral earlier this year — but not for the reason you might think.

Kendall's left leg was hidden under the folds of her dress.

If you look closely at Kendall's dress, you can see the outline of her left leg against the orange fabric. As INSIDER's Jacob Shamsian explained, the model is pointing her left knee to her right side and twisting her body around to look directly into the camera.

34/

Despite what you may think, the gray rectangles under columns A and B are the exact same color.

Discovered in 1979 by Australian psychologist Michael White, this famous effect is known as "White's Illusion." Since then, researchers have proposed several theories to explain the cause of this illusion — you can read about them here.

The two orange circles in this image are exactly the same size.

Discovered by German psychologist Hermann Ebbinghaus, this optical illusion was popularized by British psychology Edward B. Titchener in 1901.

Thus known as the "Ebbinghaus illusion" or "Titchener circles," the effect illustrates how our brain "uses context to determine the size of objects." Since the blue circles surrounding the orange circle on the left are so large, the orange circle looks smaller in comparison. Juxtapose that with the tiny blue circles on the right, and the orange circle appears relatively larger.

In case you're interested, this explanation by the Guardian breaks it down further.

Do these legs look oily or shiny to you?

An art student named Hunter Culverhouse first shared this photo on Instagram in October 2016. It went viral after people started debating whether Culverhouse's legs were covered in oil or not.

It turned out the legs were completely dry."[I] had some white paint left on my brush and put random lines on my legs," Culverhouse told INSIDER last year. While the effect was unintentional on Culverhouse's part, the white streaks made it look like a glare of light was reflecting off the student's legs.

Advertisement

39/

The red lines in this image look like they're bending slightly outward.

People eventually figured it out.

INSIDER's Jacob Shamsian broke it down last year. The woman in the middle, outlined in blue, is leaning her torso to her left and her head to her right, so it's hard to tell which pair of legs is hers.

To make things more confusing, the two women on the left are both wearing black jeans. The woman second from the left has one leg completely hidden behind the other women's legs. If you look closely, you can see a sliver of her other leg poking out.

42/

The middle of these shapes look like they're tinted by the light orange outlines, but it's an illusion.

If you look at the photo upside down, the illusion disappears.

Basically, "your brain thought the sun was in the 1:00 position," casting shadows from the upper right. However, the sun was actually casting shadows from the upper left, INSIDER's Jacob Shamsian explained.

Sign up here to get INSIDER's favorite stories straight to your inbox.